WW 3? No. WW 2 continued. It would have been Fat Men and little boys reducing Moscow, Stalingrad and Leningrad to rubble. Case closed and the example set would have prevented Mao from the ultimate takeover of China.
Not true. The US only built 2 nukes during WW. It would have taken 6 months at least build another. All the enriched uranium had already been used up. Truman would never had approved war against the USSR.
Firstly - the US had only 2 nukes - it would have taken months to create more. Secondly, it would have hurt their allies as well.
Mao was going to take over China no matter what